A conventional shock absorber includes the following: a cylinder, a piston that is slidably inserted into the cylinder, a piston rod that is inserted into the cylinder and connected to a piston, an extension-side chamber and a compression-side chamber that are partitioned by the piston within the cylinder, an intermediate tube that covers an outer periphery of the cylinder and forms a discharge passage between itself and the cylinder, an outer tube that covers an outer periphery of the intermediate tube and forms a reservoir between itself and the intermediate tube, a suction passage that permits only a flow of working oil from the reservoir toward the compression-side chamber, a rectification passage that is provided to the piston and permits only a flow of working oil from the compression-side chamber toward the extension-side chamber, and a damping force variable valve provided between the discharge passage and the reservoir.
This shock absorber is configured such that working oil flows out from within the cylinder to the reservoir through the discharge passage by the action of the rectification passage and the suction passage regardless of whether the shock absorber is extending or compressing, and a damping force exerted by the shock absorber is adjusted by adjusting a resistance imparted to the flow of working oil by the damping force variable valve (refer to JP2009-222136A).